The present disclosure herein relates to a manufacturing method of a compound semiconductor solar cell, and more particularly, to a manufacturing method of a compound semiconductor solar cell having an optical absorption layer of a high-grade copper indium gallium selenium (CIGS) thin film.
A solar cell or a photovoltaic cell is a core device of a photovoltaic system which directly converts solar light to electricity. When the solar light, which has a larger energy than the band-gap energy (Eg) of a semiconductor, is incident on a solar cell manufactured with a p-n junction semiconductor, electron-hole pairs are generated. Subsequently, electrons are gathered to an n-layer and holes are gathered to a p-layer, thus generating a photovoltage between the p-layer and the n-layer. At this time, a current will flow if a load is connected to both ends of electrodes. This is an operating principal of a solar cell.
Among the materials used for manufacturing a solar cell, since I-III-VI2 group chalcopyrite-based compound semiconductors represented by CuInSe2 have a direct transition type energy bandgap and also have about 1×105 cm−1 of an optical absorption coefficient which is the highest value among semiconductors, even about 1-2 μm thickness of a thin film can be manufactured into a highly efficient solar cell, and these compound semiconductors have characteristics of very good electro-optical stability in the long term. Therefore, compound semiconductors may substitute a high-priced crystalline silicon solar cell such that these are focused as materials for a low-priced and highly efficient solar cell which can radically improve the economy of a photovoltaic system.
A CIGS thin film solar cell has high efficiency and excellent stability such that it was first studied for a highly efficient lightweight solar cell in space applications capable of replacing a typical single crystal silicon solar cell (20 W/kg). The power generation amount per unit weight is also about 100 W/kg currently in single junction, which is extremely superior to about 20-40 W/kg of typical silicon (Si) or gallium arsenide (GaAs) solar cell.